1. Technical Field of the Invention
The present invention relates to a technology for copying a printed original color image, and particularly, to a technology for correcting colors of an original color image so that the color image can be copied with accurate colors.
2. Related Art
In line with advancement of digital technology represented by a computer, today, it has become possible to easily print color images of high quality in typical homes. For example, it is possible to carry out high quality color printing of images prepared by a computer and images captured by a digital camera, using a home color printer.
As a matter of course, the format for handling color images in a device on the side of generating color image data such as a computer, a digital camera, etc., is greatly different from that on the side of printing color images such as a color printer. That is, while the computer and digital camera express color images based on RGB image data in which gradation values of respective colors of RGB called three primary colors of light, the color printer prints color images using a plurality colors of ink or toner of C (Cyan), M (Magenta), Y (Yellow) and K (Black). Therefore, when printing color images, after the RGB image data are converted to an expression format consisting of respective colors of CMYK by applying a predetermined image processing to the RGB image data on the computer, data thus obtained are supplied to a color printer, whereby color printing is executed.
Further, in recent years, such a color printer in which a function of executing an image processing is internally incorporated, and a so-called scanner function of generating RGB image data by reading original color images is incorporated has been developed. A color printer called a hybrid machine can be used as if it is a color copier, wherein image data read from original color images are subjected to an image processing and color images are printed.
Herein, after any one of various types of color printers calculates the adhesion amounts of ink or toner of respective colors of CMYK by applying an image processing to the RGB image data, it executes color printing by adhering a calculated amount of ink or toner onto a printing medium by any method of ejecting ink drops or utilizing electrostatic force. Therefore, it becomes impossible to adhere ink or toner by the calculated amounts thereof through a longer period of use, wherein a difference is brought about between the calculated amounts and the actual adhesion amounts, and color printing is not executed with accurate colors any longer.
Also, due to unevenness in production, strictly speaking, there is a difference in the adhesion amounts of ink and toner in individual color printers. Therefore, various types of technologies have been proposed, which correct the amounts of ink or toner to be adhered onto a printing medium to proper amounts by correcting the calculated amounts obtained in the image processing. Such technologies are disclosed, for example, in Japanese Patent Publication Nos. 9-172545A (JP-A-9-172545) and 9-207388A (JP-A-9-207388).
However, in a case of copying original color images, there is still a problem in that even if correction is executed by applying one of the proposed technologies, it is not always possible to copy original color images with correct colors.